Hydrocarbon steam reforming and methanation catalysts

ABSTRACT

A catalyst consisting essentially of nickel, a promoter selected from the group consisting of barium and uranium and a calcium phosphate support having a Ca:P atomic ratio in the range of 1.4:1 to 2.3:1, is formed by impregnating a calcium phosphate gel with suitable compounds of nickel and either barium or uranium. The resulting catalysts are useful in steam reforming processes for producing methane.

This invention relates to novel catalytic materials and to catalyticprocesses. In one aspect this invention relates to novel catalyticmaterials. In another aspect this invention relates to the preparationof novel catalytic materials. In yet another aspect this inventionrelates to catalytic conversion processes.

Utility companies which distribute gas for household or other use havean increasingly acute need for an economical means of supplying gasduring peak-load periods. During cold weather, for example, demand maybe double or triple the volume used on a mild day. In many instances,the peak-load demand is met by adding propane-air mixtures to the gas.Because the quantity of propane-air that can be blended is limited,there is a need for an economical process that can be used to supplypeak-load demand.

The reforming of paraffinic hydrocarbons with steam has become a wellestablished process. The process produces mixtures of methane, hydrogen,oxides of carbon and small quantities of higher hydrocarbons such asethane. Various catalysts are known or such reforming processes;however, relatively few such catalysts have been able to maintain theiractivity for a sufficiently long period to make their use practical.

Methanation by steam reforming carbon monoxide is also a well knownprocess. The process produces a mixture of methane, carbon monoxide,carbon dioxide and hydrogen. Various catalysts are known for suchmethanation processes, however, many such catalysts produce methanecontaining an undesirable amount of carbon monoxide which can bedifficult to separate. Further, carbon monoxide in admixture withmethane is highly undesirable because of the high toxicity of the carbonmonoxide in the event leaks occur in supply lines or in storagecontainers.

It is an object of this invention to provide a new and improved catalystuseful for steam reforming.

Another object is to provide an improved process for making a catalyst.

Yet another object is to provide a process for steam reforminghydrocarbon materials to a methane-containing gas.

A further object is to provide a process for methanation by steamreforming carbon monoxide.

Other objects, aspects and advantages of this invention will be readilyapparent to those skilled in the art from the reading of the followingdisclosure and appended claims.

In accordance with the present invention there is provided a catalystcomposition consisting essentially of nickel, a promoter metal selectedfrom the group consisting of barium and uranium, combined oxygen and acalcium phosphate support having a Ca:P atomic ratio in the range of1.4:1 to 2:3:1.

The catalyst compositions of this invention contain calcium, phosphorus,nickel and barium or uranium in the following amounts, expressed interms of weight percent based upon the weight of the total catalyst:

    ______________________________________                                                   Broad      Preferred                                               ______________________________________                                        Calcium      5-35         10-25                                               Phosphorus   2-20          5-15                                               Nickel       10-50        20-40                                               Barium       1-20         2.5-18                                              Uranium      2-40         10-30                                               ______________________________________                                    

The difference between the sum of the percentages of the above-namedelements and 100 percent is made up by the oxygen content of thecatalyst in amounts sufficient to satisfy the valences of each of theelements in the catalyst.

In a presently preferred embodiment the support material has a Ca:Patomic ratio in the range of 1.5:1 to 1.8:1.

In a more preferred embodiment the support material has a Ca:P atomicratio of 1.67 which corresponds to calcium hydroxyapatite, Ca₅(OH)(PO₄)₃.

The catalyst compositions of this invention are prepared by firstpreparing the calcium phosphate support. An aqueous solution of asoluble calcium compound is admixed with a soluble phosphate compound toform a calcium phosphate gel having a Ca:P atomic ratio in the range of1.4:1 to 2.3:1.

Suitable calcium compounds include calcium acetate, calcium formate,calcium isobutyrate, calcium nitrate, and the like. Preferably, thecalcium salt is one in which the anion portion is decomposed atcalcination temperatures to a gas, leaving no undesirable residue.Suitable phosphate compounds include ammonium and Group Ia phosphatessuch as monohydrogen ammonium orthophosphate, sodium orthophosphate,monohydrogen sodium orthophosphate, monohydrogen sodium orthophosphate,dihydrogen sodium orthophosphate, trisodium phosphate, potassiumorthophosphate, monohydrogen potassium orthophosphate, dihydrogenpotassium orthophosphate, potassium pyrophosphate and the like.

In a presently preferred embodiment, all the phosphorus is combined withthe calcium, none of the phosphorus being available for combination withthe nickel or the promoter metals.

In one embodiment of this invention, the thus-prepared calcium phosphategel is first combined with at least one of barium or uranium. The gel isfiltered and washed, then reslurried in distilled water. Approximatelyone-half the desired amount of promoter metal in aqueous solution of asoluble promoter compound is added to the slurried gel. The mixture isallowed to stand for a period of time sufficient to ensure substantialuptake of the promoter in the wet gel. In general, this mixture shouldstand, with occasional stirring, for a period ranging from about 4 hoursto about 4 days. This period may be shorter or longer, depending uponthe promoter compound employed and the dilutions of the support gel andthe promoter solution. To this mixture is added, with stirring, anaqueous solution containing a mixture of the remaining portion of thepromoter compound and a soluble nickel compound, together with analkaline solution of, for example, ammonium hydroxide, an alkali metalhydroxide or an alkali metal carbonate. The alkaline solution is addedat a rate such that the pH of the mixture is at least 7, preferably inthe range of 7 to 9. The resulting mixture is then filtered, washed,refiltered and dried in air at about 105° C.

In another embodiment of this invention, the nickel is first added tothe calcium phosphate gel by adding an aqueous solution of a solublenickel compound to the slurry of the calcium phosphate gel, withstirring, together with an alkaline solution of, for example, ammoniumhydroxide, an alkali metal hydroxide or an alkali metal carbonate tomaintain a pH of at least 7, preferably 7-9, in the resulting mixture.The nickel/calcium phosphate gel is then filtered, washed, refilteredand dried in air at about 105° C. The dried material is then impregnatedwith an aqueous solution of the promoter compound and re-dried at about105° C.

The dry catalyst material can then be crushed, or otherwise reduced togranules or small lumps and be used directly; or it can, preferably, bepulverized, such as to a particle size capable of passing a 20-40 meshscreen, and the powdered product treated with a lubricant and pressedinto the form of a pill or tablet or granule of size suitable for use asa catalyst. After forming, the catalyst material is calcined in thepresence of an oxygen-containing gas or air at a suitable calcinationtemperature in the range of about 300°-650° C for a period of 30 minutesto 10 hours, or more. Prior to use, the calcined material is reducedwith hydrogen at a temperature in the range of 300°-650° C for a periodof 30 minutes to 10 hours, or longer, if necessary. Alternatively, thedried catalyst material can be reduced, as above, without priorcalcination.

Suitable nickel compounds include nickel acetate, nickel nitrate andnickel sulfate. Suitable barium compounds include barium acetate, bariumbenzoate, barium butyrate, barium formate, barium nitrate, bariumnitrite, barium propionate, barium salicylate and the like. Suitableuranium compounds include uranyl acetate, uranyl formate, uranyl nitrateand the like.

It is also within the scope of this invention to employ soluble halidecompounds such as the nickel halides, barium halides and uranyl halides,such as the chlorides, bromides and iodides. It is further within thescope of this invention to employ calcium halide salts in preparing thesupport gel. However, due to the difficulty in removing the halideanions from the catalyst material during purification and calciningoperations, the use of such halides is preferably avoided.

The catalysts of this invention are suitable for use in hydrocarbonconversion processes. In one embodiment of this invention there isprovided a methanation process for the conversion of carbon monoxide bysteam reforming to a gas containing methane and carbon dioxide, whichcomprises contacting a mixture of carbon monoxide and steam at anelevated temperature with the catalyst of this invention. The conversionis conducted at a temperature in the approximate range of 300°-1000° F(148°-538° C), at a pressure in the approximate range of 0-2000 psig (0to 13.7 MPa) at a gaseous hourly space velocity (GHSV) for carbonmonoxide in the approximate range of 100 to 10,000 and a carbon monoxideto steam mole ratio in the approximate range of 2:1 to 1:5.

It is presently preferred that the methanation process be conducted at atemperature in the approximate range of 400°-800° F (204°-427° C) at apressure in the approximate range of 100 to 1,000 psig (0.689 to 6,89MPa) and a carbon monoxide to steam mole ratio in the approximate rangeof 1:1 to 1:3.

It is presently preferred that the nickel on calcium phosphate catalystused for methanation by reaction of CO and steam be promoted withuranium.

In another embodiment of this invention there is provided a process forsteam reforming a hydrocarbon feedstock which comprises contacting ahyrocarbon feedstock having from 2 to 15 carbon atoms per molecule withsteam and the catalyst of this invention at an elevated temperature. Thereforming is conducted at a temperature in the approximate range of650°-1200° F (343°-649° C) at a pressure in the approximate range of 0to 2000 psig (0 to 13.7 MPa) at a liquid hourly space velocity (LHSV)for the feedstock in the approximate range of 0.1 to 10 and a steam tohydrocarbon weight ratio in the approximate range of 1:1 to 10:1.

It is presently preferred that the reforming process be conducted at atemperature in the approximate range of 700°-1000° F (371°-538° C), at apressure in the approximate range of 100 to 1,000 psig (0.689 to 6.89MPa) at an LHSV for feedstock in the approximate range of 1 to 5 and asteam to feedstock weight ratio in the approximate range of 1:1 to 5:1.

In a presently preferred embodiment the nickel on calcium phosphatecatalyst used for steam reforming of hydrocarbons in accordance withthis invention is promoted with barium.

Steam reforming of hydrocarbons, according to the invention, results inthe formation of a gaseous product rich in methane.

The hydrocarbon feedstocks processable to methane-rich productsaccording to the invention comprise hydrocarbons having from 2 to 15carbon atoms per molecule. Such feedstocks preferably containpredominately paraffinic hydrocarbons such as propane, butane, hexane,cyclohexane, octane, cyclooctane, decane, dodecane, pentadecane and thelike.

The carbon dioxide produced in either of the above processes can beremoved by conventional methods, such as by absorption in an aminesolution.

The following examples illustrate the invention:

EXAMPLE I

Five catalysts having the general configuration as nickel promotedcalcium phosphate materials were prepared in different manners andsubsequently employed for the steam reforming of cyclohexane. Catalyst Awas prepared according to the method of this invention. The remainingcatalysts are control catalysts. Catalyst B was prepared by a prior artmethod. Catalysts C, D and E were prepared by coprecipitating the nickelwith the calcium phosphate.

Catalyst A was prepared by adding an aqueous solution of dipotassiumhydrogen phosphate (1.0 mole) with vigorous stirring to an aqueoussolution of calcium acetate (1.67 moles) to obtain a calcium phosphategel having a Ca/P atomic ratio of 1.67. After standing overnight, thegel was recovered by filtration and washed by slurrying in a 3500 mlportion of water and filtered. The wash treatment was done three times.Finally, the filter cake was additionally washed by pulling 10 liters ofdistilled water through it. About 1/4 of the wet cake was reslurried in1000 ml of distilled water and to the stirred slurry was added 16 g ofbarium nitrate dissolved in 300 ml of distilled water. The mixture wasallowed to stand for 2 days with occasional stirring. Then to thewell-stirred slurry was slowly added a mixture of 145 g nickel nitrateand 16 g barium nitrate dissolved in 600 ml of hot distilled water and100 g potassium carbonate dissolved in 250 ml of distilled water. Theresulting mixture was filtered to obtain a cake which was reslurried inabout 3500 ml of distilled water and filtered. This operation wasrepeated and finally about 3 liters of distilled water was pulledthrough the filter cake. The cake was dried overnight at 220° F, crushedto pass a 40 mesh screen and calcined in air at 800° F for 3 hours. Thecooled product was mixed with 3 weight percent polyethylene powder andpilled to 1/8-inch size at 100 psig. The pills were heated at about 800°F in hydrogen for about 20 minutes to obtain the finished catalyst. Thisinvention catalyst, as analyzed, contained 16.3 weight percent bariumand 26.9 weight percent nickel based on the total weight of the catalystcomposite. The surface area of the catalyst was about 80 square metersper gram, as determined by nitrogen absorption, the pore volume wasabout 0.2 ml per gram as determined by water absorption, and theapparent bulk density was 0.94 gram per ml.

Catalyst B is a control catalyst made in the manner described in U.S.Pat. No. 3,149,081 by adding a solution obtained by dissolving 110 gnickel carbonate to a total of 324 g of 85 percent H₃ PO₄ contained in736 ml of hot water. The clear dark green solution was added withvigorous stirring to a slurry of 352 g of calcium hydroxide in water.The atomic ratio of Ca to P was about 1.67 to correspond to theformation of calcium hydroxyapatite. After standing overnight, the gelwas filtered and dried overnight at 220° F. The product was crushed topass a 40 mesh screen and resulting material was calcined at 800° F inair for 2 hours. The cooled product was mixed with 4 weight percentpolyethylene powder, pilled and reduced in hydrogen as described forcatalyst A. Analysis showed the catalyst to contain 8.9 weight percentnickel. The surface area was about 61 square meters per gram and thepore volume was about 0.6 ml gram.

Catalysts C, D and E are control catalysts made by modifying the methodused in preparing catalyst B to incorporate more nickel and to addbarium as a promoter. In these preparations, a solution containingnickel nitrate and orthophosphoric acid was added to a slurry of calciumhydroxide in water. In each instance, a 1:2:3.68 mole ratio of H₃ PO₄ toNi(NO₃)₂ to Ca(OH)₂ was used. The manner of adding the barium promoterwas somewhat different in each preparation, however. For catalyst C, a4:1 nickel to barium atomic ratio was used, half the barium being addedas barium nitrate to the nickel nitrate-phosphoric acid solution and theother half impregnated as barium acetate solution onto the dried andcalcined product. For catalyst D, a 4:1 nickel to barium atomic ratiowas used but the entire amount of barium was added to the nickelnitrate-phosphoric acid solution prior to adding the total solution tothe calcium hydroxide. For catalyst E, a 5:1 nickel to barium atomicratio was employed and the barium as a solution of barium acetate wasadded to the mixture resulting from the addition of the nickelnitrate-phosphoric acid solution to the calcium hydroxide slurry.Catalyst C was dried, crushed, sieved and calcined in air at 800° F inthe form of 10-20 mesh material. This catalyst was not pilled. CatalystD was dried and calcined in a similar manner but 10-40 mesh material wasretained as the final catalyst. This catalyst was not pilled. Catalyst Ewas treated similarly to catalyst D except it was used in the form ofmaterial passing a 60 mesh screen. Catalyst C was analyzed and found tobe composed of 10.3 weight percent barium, 26.8 weight percent nickel,15.8 weight percent calcium and 7.1 weight percent phosphorus. Thesurface area of the catalyst was about 51 square meters per gram and ithad a pore volume of about 0.3 ml per gram. Catalyst D was analyzed andfound to be composed of 1.03 weight percent barium, 34.5 weight percentnickel, 15.8 weight percent calcium and 9.3 weight percent phosphorus.The surface area of the catalyst was about 114 square meters per gramand the pore volume was about 0.6 ml per gram. Catalyst E was analyzedand found to be composed of 2.52 weight percent barium. 27.8 weightpercent nickel, 18.8 weight percent calcium and 7.5 weight percentphosphorus. The surface area of the catalyst was about 74 square metersper gram and the pore volume was about 0.5 ml per gram.

EXAMPLE II

The catalysts of Example I were tested for steam reforming cyclohexanein a fixed bed reactor at about 850° F and a pressure of 300 psig (about2.067 MPa). The cyclohexane was supplied to the reactor at a weighthourly space velocity (WHSV) of 2. The steam to hydrocarbon weight ratiowas about 1.6:1.

Each catalyst was charged to a reactor and reduced with hydrogen forabout 30 minutes while bringing the reactor up to reforming temperature.

The following data were obtained:

                  Table I                                                         ______________________________________                                        Run    Catalyst  Ni, wt. % Ba, wt. %                                                                             Useful Life                                ______________________________________                                        1      A         26.9      16.3    2550                                       2      B          8.9      None     <40                                       3      C         26.8      10.3     150                                       4      D         34.5       1.0     800                                       5      E         27.8       2.5    1050                                       ______________________________________                                    

In the above table, the term "Useful Life" is an expression of theweight of cyclohexane converted per unit weight of catalyst. Each of theabove runs was terminated when the conversion of feedstock dropped belowabout 99 percent. During the first 90 percent of Run 1, conversion ofcyclohexane was in excess of 99.5 percent with a typical gas analysis of8.5 volume percent hydrogen, 0.5 volume percent CO, 24 volume percentcarbon dioxide and 67 volume percent methane. On the last day of therun, the conversion was 98.2 percent with the gas analysis showing 11.2volume percent hydrogen, 0.5 volume percent CO, 24 volume percent carbondioxide and 64.3 volume percent methane.

EXAMPLE III

Catalyst F was prepared according to the method of this invention bymixing together aqueous solutions of calcium nitrate (0.375 mole) anddipotassium hydrogen phosphate (0.25 mole) to make a gel in which theatomic ratio of Ca to P was 1.5:1. To the gel was added 1 mole ofpotassium hydroxide in 300 ml of water followed by the slow addition of0.5 mole nickel nitrate dissolved in 400 ml of water. An additional 0.36mole of KOH dissolved in 300 ml of water was then added to the creamyprecipitate with continued stirring for 30 minutes more. The nickelhydroxide-calcium phosphate gel was filtered, washed twice byreslurrying in water and filtering and the cake was dried at 220° F. Thedry cake was sieved through 40 mesh giving 99 g of dry material.Ninety-five grams of this material was impregnated with an aqueoussolution containing 9.3 grams of barium acetate and the resulting pastewas redried at 220° F for 16 hours. The dry powder was pilled to1/8-inch tablets using 3 weight percent graphite as a die lubricant. Thepills were reduced in hydrogen at 700° F for 2 hours. The final catalystwas analyzed and found to be composed of 6.9 weight percent barium, 33.2weight percent nickel, 15.3 weight percent calcium and 9.3 weightpercent phosphorus. The surface area of the catalyst was about 123square meters per gram.

The pilled catalyst was tested for steam reforming of cyclohexane in thereactor previously used. A 1.1 WHSV hydrocarbon feed rate was used at atemperature of 800°-880° F, pressure of 300 psig and a weight ratio ofsteam to hydrocarbon of 2:1. Complete conversion of the cyclohexane wasachieved over the 350 hour test period. Typical effluent compositions atthe end of 17 hours and 324 hours are shown.

                  Table II                                                        ______________________________________                                        Component, Mole %                                                                            17 hours     324 hours                                         ______________________________________                                        Hydrogen        9.86        10.63                                             Carbon monoxide                                                                               0.03         0.14                                             Carbon dioxide 23.26        23.15                                             Methane        66.85        66.08                                             ______________________________________                                    

Consideration of the test results shows that catalysts prepared in themanner of the invention are effective in steam reforming ofhydrocarbons.

EXAMPLE IV

Catalyst G was prepared according to the method of this invention byforming a calcium phosphate gel by mixing together with vigorousstirring aqueous solutions containing 167 g calcium acetate in onesolution and 87 g dipotassium hydrogen phosphate in the other. Theatomic ratio of calcium to P was 1.67:1. The gel was filtered,reslurried three times in water, filtering each time, and given a finalwash by pulling about 1.5 liters of water through the filter cake. Thecake was then reslurried in water and to it was added an aqueoussolution containing 62 g UO₂ (NO₃)₂.sup.. 6H₂ O dissolved in water andthe mixture was allowed to stand overnight. The mixture was thenfiltered (all the yellow color was now in the precipitate). The filtercake was reslurried in water and to the slurry while maintainingvigorous stirring was slowly and simultaneously added an aqueoussolution containing 290 g of Ni(NO₃)₂.sup.. 6H₂ O and 62 g of UO₂(NO₃)₂.sup.. 6H₂ O, and an aqueous solution containing 150 g of KOH. Theresulting mixture was filtered to obtain a filter cake which wasreslurried three times in water, filtering each time, and the cake wasgiven a final wash by pulling 2 liters of water through it. The wet cakewas dried at 220° F. The dried cake was crushed and sieved. The finalcatalyst was calculated to contain 26.8 weight percent uranium, 26.6weight percent nickel, 14.9 weight percent calcium and 6.9 weightpercent phosphorus, based on theoretical considerations.

The catalyst in the form of 60-200 mesh particles was charged to afluidized bed reactor and the reactor was heated to 600° F (315° C) andpressured to 150 psig with hydrogen to reduce the catalyst. The heatingtime in this step was 30 minutes. The hydrogen flow was discontinued anda mixture of carbon monoxide and water was introduced as feed. Duringthe run, pressure was varied from 150 to 300 psig, temperature rangedfrom 550° to 800° F, the mole ratio of water to carbon monoxide wasabout 3:1 and a gaseous hourly space velocity of carbon monoxide rangingfrom about 1200 to 2000 was employed. Almost complete conversion ofcarbon monoxide was obtained, i.e., effluent analysis showed a carbonmonoxide content ranging from about 0.04 mole percent or less. Theproduct ratios on a dry basis varied somewhat with pressure andtemperature but generally fell in the ranges:

    ______________________________________                                        Hydrogen          2 - 18 mole percent                                         Carbon dioxide    65 - 75 mole percent                                        Carbon monoxide   0.01 - .04 mole percent                                     Methane           15 - 25 mole percent                                        ______________________________________                                    

The product gas can be treated conventionally to remove carbon dioxide(by absorption in amine solutions) to obtain a final product which wouldbe fungible with natural gas.

It will be evident to those skilled in the art that variousmodifications of this invention can be made, or followed, in the lightof the foregoing disclosure and discussion, without departing from thespirit or scope thereof.

What is claimed is:
 1. A catalyst composition consisting essentially ofnickel, a metal selected from the group consisting of barium anduranium, combined oxygen and a calcium phosphate support having a Ca:Patomic ratio in the range of 1.4:1 to 2.3:1, wherein the compounds arepresent in approximate amounts, as follows:

    ______________________________________                                        Calcium         5 to 35,                                                      Phosphorus      2 to 20,                                                      Nickel          10 to 50, and either                                          Barium          1 to 20, or                                                   Uranium         2 to 40,                                                      ______________________________________                                    

all said amounts expressed in terms of weight percent, based upon theweight of the total catalyst.
 2. The composition of claim 1 wherein thecomponents are present in approximate amounts, as follows:

    ______________________________________                                        Calcium         10 to 25,                                                     Phosphorus      5 to 15,                                                      Nickel          20 to 40, and either                                          Barium          2.5 to 18, or                                                 Uranium         10 to 30,                                                     ______________________________________                                    

all said amounts expressed in terms of weight percent, based upon theweight of the total catalyst.
 3. The composition of claim 1 wherein saidCa:P ratio is about 1.67:1.
 4. A composition in accordance with claim 3containing about 26.9 weight percent nickel and about 16.3 weightpercent barium, based upon the weight of the total catalyst.
 5. Thecomposition of claim 1 wherein said Ca:P ratio is about 1.5:1.
 6. Acomposition in accordance with claim 5 containing about 33.2 weightpercent nickel and about 6.9 weight percent barium, based on the weightof the total catalyst.
 7. A composition in accordance with claim 3containing about 26.6 weight percent nickel and about 26.8 weightpercent uranium, based on the weight of the total catalyst.
 8. A methodfor preparing a catalyst composition consisting essentially of nickel, apromoter selected from the group consisting of barium and uranium,combined oxygen and a calcium phosphate support having a Ca:P atomicratio in the range of 1.4:1 to 2.3:1 which comprises admixing an aqueoussolution of a soluble calcium salt and an aqueous solution of a solublephosphate salt to form a calcium phosphate gel having a Ca:P atomicratio in the range of 1.4:1 to 2.3:1, introducing into said gel anaqueous solution of nickel and an aqueous solution of barium or uranium,recovering the promoted gel, drying said promoted gel and thereafterheating the catalyst composition at a temperature in the approximaterange of 300°-650° C.
 9. The method of claim 8 wherein the componentsare present in the final catalyst composition in approximate amounts asfollows:

    ______________________________________                                        Calcium         5-35,                                                         Phosphorus      2-20,                                                         Nickel          10-50, and either                                             Barium          1-20, or                                                      Uranium         2-40,                                                         ______________________________________                                    

wherein all said amounts are expressed in terms of weight percent, basedupon the weight of total catalyst.
 10. The method of claim 8 wherein afirst portion of said promoter is introduced to said gel, the resultingmixture is allowed to stand for a period in the range of about 4 hoursto about 4 days, to the thus partially promoted gel is introduced theremaining portion of said promoter and said nickel compound, and whereinsaid catalyst composition is thereafter recovered.
 11. The method ofclaim 8 wherein said nickel solution and said promoter solution aresimultaneously introduced to said gel.